The purpose of this study is to evaluate the ability of PET/MRI (Positron Emission Tomography/Magnetic Resonance Imaging) to give physicians preoperative information about specific sites in the body that the endometrial cancer may be present. If the PET/MRI is accurate and successful in providing this information, then women in the future may be able to have less extensive surgery for their endometrial cancer after evaluation with PET/MRI.